Sleep Perception in Obstructive Sleep Apnea: A Study Using Polysomnography and the Multiple Sleep Latency Test

BACKGROUND AND PURPOSE: Discrepancies between objectively measured sleep and subjective sleep perception in patients with insomnia have been reported. However, few studies have investigated sleep-state misperception in patients with obstructive sleep apnea (OSA). We designed this study to 1) delineate the factors that could affect this discrepancy and 2) infer an underlying mechanism in patients with OSA. METHODS: We recruited patients who visited our sleep clinic for the evaluation of their snoring and/or observed OSA. Participants completed a structured questionnaire and underwent overnight polysomnography. On the following day, five sessions of the multiple sleep latency test (MSLT) were applied. We divided the patients into two groups: normal sleep perception and abnormal perception. The abnormal-perception group included patients whose perceived total sleep time was less than 80% of that measured in polysomnography. RESULTS: Fifty OSA patients were enrolled from a university hospital sleep clinic. Excessive daytime sleepiness, periodic limb movement index (PLMI), and the presence of dreaming were positively associated with poor sleep perception. REM sleep near the sleep termination exerted important effects. Respiratory disturbance parameters were not related to sleep perception. There was a prolongation in the sleep latency in the first session of the MSLT and we suspected that a delayed sleep phase occurred in poor-sleep perceivers. CONCLUSIONS: As an objectively good sleep does not match the subjective good-sleep perception in OSA, physicians should keep in mind that OSA patients who perceive that they have slept well does not mean that their OSA is less severe.

Cost-benefit Analysis of Sodium Intake Reduction Policy in Korea / 대한지역사회영양학회지

It is well established that excessive sodium intake is related to a higher incidence of chronic diseases such as hypertension, stroke, coronary heart disease, cardiovascular disease and gastric cancer. Although the upper limit of the current sodium intake guideline by WHO is set at 2,000 mg/day for adults, sodium intake of Koreans is well over 4,700 mg/capita/day implying an urgent need to develop and implement sodium intake reduction policy at the national level. This study investigated the cost-effectiveness of the sodium intake reduction policy, for the first time, in Korea. Analyses were performed using most recent and representative data on national health insurance statistics, healthcare utilization, employment information, disease morbidity/mortality, etc. The socioeconomic benefits of the policy, resulting from reduced morbidity of those relevant diseases, included lower medical expenditures, transportation costs, caregiver cost for inpatients and income losses. The socioeconomic benefits from diminished mortality included reductions in earning losses and welfare losses caused by early deaths. It is estimated that the amount of total benefits of reducing sodium intake from 4.7 g to 3.0 g is 12.6 trillion Korean Won; and the size of its cost is 149 billion Won. Assuming that the effect of sodium intake reduction would become gradually evident over a 5-year period, the implied rate of average return to the sodium reduction policy is 7,790% for the following 25 years, suggesting a very high cost-effectiveness. Accordingly, development and implementation of a mid-to-long term plan for a consistent sodium intake reduction policy is extremely beneficial and well warranted.